Loads From Currents and Waves on Net Structures

2012 ◽  
Author(s):  
Are Johan Berstad ◽  
Jørgen Walaunet ◽  
Line Fludal Heimstad
Keyword(s):  
Test Cases ◽  
Fish Farms ◽  
Flow Angle ◽  
Reynolds Number Flow ◽  
Load Calculation ◽  
Aquaculture Industry ◽  
Number Flow ◽  
Net Cages ◽  
Almost All ◽  
Good Agreement

The aquaculture industry has increased rapidly the last 20 years. In almost all fish farms, the fish is held captured in net cages. Net structures are built up with twines as shown in Figure 1. Various parameters of importance for the loads to nets such as solidity, Reynolds number, flow angle relative to mesh and increased flow around twines compared to single twines. This paper outlines such effects. This paper consider loads to net panels considering the net a sum of twines and then sum the forces twine by twine. Based on this approach the paper presents a calculation method for net meshes. The presented load formulation is valid for rectangular and diamond shaped meshes and is valid for any 3D orientation of flow relative to mesh. The presented method for load calculation includes methodology for deriving the forces to a net structure based on knowledge of drag resistance for an individual twine. This methodology is compared with other published formulae and empirical data. A formula is presented based on a twine in wake consideration. The presented formula is compared to measurements for test cases both in terms of a net panel and for a full cage model. Results show good agreement.

Low-Reynolds-number flow around an oscillating circular cylinder at low Keulegan–Carpenter numbers

1998 ◽  
Vol 360 ◽  
pp. 249-271 ◽  
Author(s):  
H. DÜTSCH ◽  
F. DURST ◽  
S. BECKER ◽  
H. LIENHART
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Time Step ◽  
Time Resolved ◽  
Reynolds Number Flow ◽  
Line Force ◽  
Number Flow ◽  
Weakly Stable ◽  
Fluid Behaviour ◽  
Good Agreement

Time-averaged LDA measurements and time-resolved numerical flow predictions were performed to investigate the laminar flow induced by the harmonic in-line oscillation of a circular cylinder in water at rest. The key parameters, Reynolds number Re and Keulegan–Carpenter number KC, were varied to study three parameter combinations in detail. Good agreement was observed for Re=100 and KC=5 between measurements and predictions comparing phase-averaged velocity vectors. For Re=200 and KC=10 weakly stable and non-periodic flow patterns occurred, which made repeatable time-averaged measurements impossible. Nevertheless, the experimentally visualized vortex dynamics was reproduced by the two-dimensional computations. For the third combination, Re=210 and KC=6, which refers to a totally different flow regime, the computations again resulted in the correct fluid behaviour. Applying the widely used model of Morison et al. (1950) to the computed in-line force history, the drag and the added-mass coefficients were calculated and compared for different grid levels and time steps. Using these to reproduce the force functions revealed deviations from those originally computed as already noted in previous studies. They were found to be much higher than the deviations for the coarsest computational grid or the largest time step. The comparison of several in-line force coefficients with results obtained experimentally by Kühtz (1996) for β=35 confirmed that force predictions could also be reliably obtained by the computations.

Numerical Simulation of the Flow of Highly Viscous Drops Down a Tapered Tube

1994 ◽  
Vol 116 (2) ◽  
pp. 172-177 ◽  
Author(s):  
R. Tran-Son-Tay ◽  
T. F. Kirk ◽  
D. V. Zhelev ◽  
R. M. Hochmuth
Keyword(s):  
Theoretical Models ◽  
Inviscid Fluid ◽  
Cortical Tension ◽  
Reynolds Number Flow ◽  
Viscous Drops ◽  
Conical Section ◽  
Viscous Drop ◽  
End Caps ◽  
Number Flow ◽  
Good Agreement

The flow of a highly viscous drop surrounded by an inviscid fluid inside a tapered tube is analyzed according to a Newtonian, liquid-drop model in which a variational method is used to simultaneously solve the hydrodynamic equations for low Reynolds-number flow and the equations for membrane equilibrium with a constant membrane tension. It is found that the flow in the end caps is plug and radial in the conical section of the drop. The results are compared to a simplified analytical theory that makes these assumptions. Very good agreement is found between the two approaches. Both approaches are used to analyze existing experimental results of passive neutrophils flowing down a tapered tube. The theoretical models give a good fit to published experimental data by Bagge et al. (1977) at driving pressures of 20 and 40 mm H2O for a membrane cortical tension of 0.024 dyn/cm and an apparent cytoplasmic viscosity of about 2400 and 1400 poise, respectively.

scholarly journals A PENDULUM-BASED MODEL FOR FLUID STRUCTURE INTERACTION ANALYSES

2007 ◽  
Vol 6 (2) ◽  
pp. 76 ◽  
Author(s):  
D. A. M. Martins ◽  
A. Silveira-Neto ◽  
V. Steffen Jr
Keyword(s):  
Fluid Structure Interactions ◽  
Present Contribution ◽  
Large Reservoir ◽  
Single Degree Of Freedom ◽  
Fluid Structure ◽  
Low Reynolds Number Flow ◽  
Reynolds Number Flow ◽  
Damped System ◽  
Number Flow ◽  
Good Agreement

In the present contribution a pendulum-based model is used to represent fluid-structure interactions. For this purpose, a theoretical and experimentalanalysis of the dynamic behavior of a viscously damped spherical non rotational single-degree-of-freedom pendulum was performed. The dampingprocess is characterized according to two different regimes: in the first, it can be seen as a viscous low Reynolds’ number flow and, in the second, it can be considered as a viscously damped system. The pendulum was tested experimentally in a large reservoir containing a Newtonian fluid for validation purposes and good agreement was found between numerical and experimental results.

Low Reynolds number flow around and heat transfer from a heated circular cylinder

2010 ◽  
Vol 1 (1-2) ◽  
pp. 15-20 ◽  
Author(s):  
B. Bolló
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Reynolds Number Flow ◽  
Two Dimensional Flow ◽  
Number Flow ◽  
Low Reynolds ◽  
Increasing Temperature

Abstract The two-dimensional flow around a stationary heated circular cylinder at low Reynolds numbers of 50 < Re < 210 is investigated numerically using the FLUENT commercial software package. The dimensionless vortex shedding frequency (St) reduces with increasing temperature at a given Reynolds number. The effective temperature concept was used and St-Re data were successfully transformed to the St-Reeff curve. Comparisons include root-mean-square values of the lift coefficient and Nusselt number. The results agree well with available data in the literature.

scholarly journals Experimental and theoretical progress in pipe flow transition

2008 ◽  
Vol 366 (1876) ◽  
pp. 2671-2684 ◽  
Author(s):  
A.P Willis ◽  
J Peixinho ◽  
R.R Kerswell ◽  
T Mullin
Keyword(s):  
Pipe Flow ◽  
Quantitative Agreement ◽  
Travelling Wave ◽  
Turbulent Pipe Flow ◽  
Transition To Turbulence ◽  
Reynolds Number Flow ◽  
Threshold Amplitude ◽  
Number Flow ◽  
The Stability ◽  
Laminar State

There have been many investigations of the stability of Hagen–Poiseuille flow in the 125 years since Osborne Reynolds' famous experiments on the transition to turbulence in a pipe, and yet the pipe problem remains the focus of attention of much research. Here, we discuss recent results from experimental and numerical investigations obtained in this new century. Progress has been made on three fundamental issues: the threshold amplitude of disturbances required to trigger a transition to turbulence from the laminar state; the threshold Reynolds number flow below which a disturbance decays from turbulence to the laminar state, with quantitative agreement between experimental and numerical results; and understanding the relevance of recently discovered families of unstable travelling wave solutions to transitional and turbulent pipe flow.

Small Reynolds Number Electro-Hydrodynamic Flow Around Drops and the Resulting Deformation

1979 ◽  
Vol 46 (3) ◽  
pp. 510-512 ◽  
Author(s):  
M. B. Stewart ◽  
F. A. Morrison
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Order Approximation ◽  
Creeping Flow ◽  
Small Reynolds Number ◽  
Zeroth Order ◽  
Regular Perturbation ◽  
Low Reynolds Number Flow ◽  
Reynolds Number Flow ◽  
Number Flow

Low Reynolds number flow in and about a droplet is generated by an electric field. Because the creeping flow solution is a uniformly valid zeroth-order approximation, a regular perturbation in Reynolds number is used to account for the effects of convective acceleration. The flow field and resulting deformation are predicted.

Low Reynolds number flow past a transverse cylinder at Mach two.

AIAA Journal ◽  
1972 ◽  
Vol 10 (10) ◽  
pp. 1381-1382
Author(s):  
CLARENCE W. KITCHENS ◽  
CLARENCE C. BUSH
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Low Reynolds Number Flow ◽  
Reynolds Number Flow ◽  
Flow Past ◽  
Number Flow ◽  
Low Reynolds
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